How to pass a System Design Interview
Preparation and candidate behavior
Slide contents
1. How to pass a System Design Interview
Preparation and candidate behavior
2. Alexander Polomodov
Role at the time · 2022
Alexander Polomodov, CTO, mobile banking and acquisition, Tinkoff
Focus — Oversaw architecture decisions
Context — Oversaw System Design Interviews · Interviewed technical leaders
Oversaw architecture decisions
Oversaw System Design Interviews
Interviewed technical leaders
3. From hiring to candidate behavior
Map of the talk
Hiring and seven steps
Requirements, boundaries, flows
Models, technology, scaling
Behavior and study paths
4. System Design targets Senior and Senior+
Junior and Middle skip this section
5. Architecture emerges one step at a time
From the prompt to follow-up questions
6. 02. Formalization
Before the first line is drawn
7. Clarify the problem first
Scenarios, scale, priorities
What is in and out
Who uses it and why
What volumes are expected
What matters most
8. Priorities direct the architecture
Sizing connects requirements to scale
9. Learn the language of requirements
Functionality and architecture qualities
UML Use Cases
User Stories and JTBD
ATAM for trade-offs
Wiegers and Eyskens
10. 03. System boundaries
The system inside its environment
11. A boundary starts with a scenario
Files, DB, API, or Messaging
12. Understand every request path
From context to load balancer
C4 System Context
REST, RPC, GraphQL, AsyncAPI
OSI, TCP/IP, DNS
HTTP/1.1–HTTP/3 and WebSockets
13. 04. Flows
Components emerge from behavior
14. The happy path reveals exceptions
Then load and failing parts
15. Trace reads and writes
Against the architecture characteristics
Trace the read path
Trace the write path
Apply the leading NFRs
Balance the read/write path
16. Choose the diagram for the question
What to study for flows
C4 shows containers
Sequence reveals interactions
Activity captures branching
IDEF0, DFD, and BPMN for flows
17. 05. Conceptual design
Solution classes come first
18. Responsibility comes before product choice
Stateful, stateless, data, and contexts
19. Connect models to storage
Data determines access
RDBMS and NoSQL classes
ER and Class Diagrams
DDD and bounded contexts
Twelve-Factor App
20. 06. Real system design
Technology, guarantees, operations
21. Technology must uphold the promise
Guarantees, capacity, failure domains
22. Design continues after launch
Operation and evolution
Logs and monitoring
Schema and data migrations
Hands-on SRE tooling
Google SRE books
23. 07. Under load
Different state, different levers
24. State determines the scaling mechanism
Orchestrators, replication, partitioning, sharding
25. Scale for real access patterns
Topology changes guarantees
Start with access patterns
Name the consistency model
Read DDIA and Database Internals
Validate with load tests
26. Lead the conversation, do not guess
Think aloud, respond to hints
27. Study along four paths
All links are in a Book Cube post
Requirements and trade-offs
Networks and integration
Data and distribution
Reliability and operations
28. Meaning first, technology second
Seven steps keep the conversation coherent
polomodov.tech
Clarify, trace flows, explain trade-offs
Alexander Polomodov, Author and speaker, ArchDays 2022
@book_cube